Japan and US probe closure of Bitcoin exchange MtGox as boss speaks out

The boss of one of the world's biggest Bitcoin marketplaces has broken his silence over its surprise suspension, just as it was revealed that Japanese and US authorities are investigating the case.

MtGox, an online exchange for the digital currency, was taken offline without explanation yesterday amid rumours of theft and insolvency. A statement was then posted on the site saying the closure was “in order to protect the site and our users”.

Today MtGox chief executive Mark Karpeles issued a statement on the site for the first time since the incident, after speculation he had left the country.

Karpeles said: "As there is a lot of speculation regarding MtGox and its future, I would like to use this opportunity to reassure everyone that I am still in Japan, and working very hard with the support of different parties to find a solution to our recent issues."

Japan’s chief cabinet secretary Yoshihida Suga has confirmed that country’s police, Finance Ministry and financial watchdog are all investigating the case, adding: “Once we have full knowledge of what happened, we will take action if necessary.”

Meanwhile, US media has reported that prosecutors in New York served the company with a subpoena there shortly before its closure.

Prior to the platform’s suspension, what appeared to be a leaked document from the Tokyo-based company was published online, claiming a security fault allowed hackers to steal 744,408 Bitcoin, worth about $350m (£210m) at Monday’s trading prices.

The document claimed that as a result MtGox was close to bankruptcy. MtGox handled as much as 70% of the global Bitcoin trade at its height.